Play only one action at a time
Mute the NLA



Can mute the entire NLA stack using toggle, as shown in image, or via scripting by setting the object's animation data use_nla property. When muted will only evaluate the active action. I call this the one in the "slot", that displays keyframes in action editor / dope sheet. 

&gt;&gt;&gt; C.object.animation_data.use_nla
True

&gt;&gt;&gt; C.object.animation_data.use_nla = False
&gt;&gt;&gt; C.object.animation_data.use_nla
False


A muted NLA stack is a convenient way to store actions with an association to their target object, mesh, shape etc.

Note also: NLA tracks can be muted individually via the similar mute button on each track.